The innovative use of a synthetic peptide to modulate epithelial or endothelial cell-cell interactions is proposed for the augmentation of drug- or gene-based therapeutic interventions. Cell monolayers are a major obstacle to delivering drugs to selected locations throughout the body. Transient access to these compartments would provide physicians with an additional means to diagnose and treat debilitating and life-threatening disorders. In developing a new therapeutic approach for treating cystic fibrosis, Nacelle Therapeutics, Inc. identified a small group of peptides displaying an unusual activity. This subset of channel-forming peptides transiently reduces electrical resistance (a measure of barrier integrity) across a transformed epithelial cell monolayer (MOCK cells). This observation was outside of the targeted outcome, but its therapeutic potential was immediately recognized. Preliminary experiments indicated peptide-induced paracellular permeability to small (<10 kDa) but not large dextrans. We now propose to explore the potential applications of these peptides as transient modulators of epithelial and endothelial barriers. Over the next six months, we will identify the scope of epithelia that are amenable to such modulation. In vitro efficacy will be tested in both human and non-human epithelia from a variety of tissues including airway, intestine and vas deferens. Endothelial cell monolayers derived from both human and non-human vessels will also be tested to determine the scope of therapeutic potential in these tissues. The outcomes of these studies will identify specific target tissues that can be therapeutically modulated by this family of peptides. The mechanism by which the peptides cause the resistance loss will also be investigated. Two potential mechanisms will be tested: one, a signal transduction, receptor mediated process that is triggered by the binding of the peptide to a putative, receptor such as that seen in with ZOT resistance modulation, or two, a direct chloride conductance mediated process where the induction of large chloride fluxes by the channel forming peptides alone induce the resistance loss. In a Phase II application drug uptake studies will be monitored using both in vitro and in vivo systems.